Flame stabilizer for high velocity gas streams



Jan. 27,1959 2,870,604

FLAME STABILIZER FOR HIGH VELOCITY GAS STREAMS E. W. CONRAD Filed April 27, 1955 INVENTOR EARL W CONRAD BY a (2i ATTORNEYS United States Patent Ofiice Patented Jan, 27 ,1959

United States of America as represented by the Secretary of the Navy Application April 27, 1955, Serial No; 504,388 9 Claims. (Cl. 60'3 9;72) (Granted tinder rare as, U. s. cede 1952 see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to an improved flame stabilizer for high velocity gas streams and more particularly to an improvement in the construction of a flame gutter for jet engines wherein the local gas velocity is decreased by an obstruction adjacent the gutter.

In jet engines, fuel is injected into air flowing through the engine, and the mixture ignited. Due to the high velocity of the gas stream difliculty has been encountered in maintaining the flame, so that further consideration of the problem led to V-shaped flame gutters placed in the air stream with the apex of the V facing upstream. However, this solution has not proved to be entirely satisfactory at very high gas velocities.

The present invention overcomes these and other deficiencies of the prior art and in addition provides for greater dependability of operation with a minimum weight penalty.

An object of the present invention is the provision of an improved flame gutter to better hold and stabilize the flame in a jet engine at very high flow velocities Another object is to provide an improved flame gutter which will hold and stabilize the flame in a jet engine at extremely low pressures.

A further object is to provide means in association with a flame gutter to reduce the local velocity of the gas stream laterally adjacent the gutter.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a perspective view, with parts broken away of a jet engine equipped with a preferred embodiment of the invention;

Fig. 2 is a cross-sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view of a modification of the invention;

Fig. 4 is a cross-sectional view illustrating another modification of the invention, and,

Fig. 5 is a cross-sectional view of still another modification of the invention.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a jet engine comprising a cylindrical or conical inner body 12 and an outer body 14. Between bodies 12 and 14 air mixed with fuel flows at a very high vleocity and extremely low pressure in the direction of the arrows. A V-shaped flame gutter 16 extends across the gas stream between the bodies 12 and 14, the apex of the gutter 16 pointing upstream. The flame is held on the trailing edges of the gutter 16. Extending outwardly and forwardly from each of the trailing edges of the gutter 16 are a coarse screen 18 and a 2 fine screenztl, e fine screen 20 extending onlyabout half the length of the coarse screen Preferably, the forward edge of coarse screen-13 is held in a brace 22, for support.

In Fig. 3 there is shown a modification, wherein there extends directly out from each of the trailing edges of a gutter 16 a coarse screen 24 behind which: is a fine screen 26, extending approximately half the distance of coarse" screen 24. The outer edge of coarse screen 24 is held by a brace 28. v i

In themodification shown in Fig. 4, a coarse screen 30 extends outwardly from each of the trailing edgesof gutter 16, and is held by a brace 32. In front of, and hence supported by coarse screen 30 a fine screen 34, extendiiig approximately half the distance of coarse screen 30 The screens 3t? and 34 extend in the same planes as the sides of the gutter 16.

In Fig. 5, there is shown a gutter 16 with screens upstream of it. A coarse screen 36 extends transversely across the stream of gas, between two braces 38. In front of the coarse screen 36 is a fine screen 40, which extends across approximately the middle half of the coarse screen 36.

In operation, each of the screen arrangements shown causes the gas laterally adjacent the trailing edges of the gutter 16 to be slowed down. Otherwise stated, while the main gas stream has a very high velocity, the local velocity laterally adjacent the gutters is substantially reduced, thus improving greatly the action of the gutter 16. A gradual velocity gradient laterally away from the trailing edge of gutter 16 is obtained, which is highly desirable for flame propagation.

It will be understood that the present invention can be used wherever flame holder gutters are used, such as in ram jets or after burners, and with other shaped flame stabilizers.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a jet engine, a flame stabilizer comprising a structural member extending transversely of a high velocity gas stream, said structural member having at least one trailing edge extending transversely of said gas stream, and screen means associated with said flame stabilizer to reduce the local velocity in a zone of the stream laterally adjacent said structural member, whereby a gradual velocity gradient is produced and maintained between the local and main stream velocities along substantially the entire length of said trailing edge.

2. in a jet engine, a flame stabilizer comprising a V- shaped gutter extending transversely of a high velocity gas stream, said gutter having trailing edges extending transversely of said gas stream, and screen means associated with said gutter to reduce the local velocity in a zone of the stream laterally adjacent said gutter, whereby a gradual velocity gradient is produced and maintained between the local and main stream velocities along substantially the entire lengths of said trailing edges.

3. In a jet engine, a flame stabilizer comprising a V- shaped gutter extending transversely of a high velocity gas stream, the apex of said gutter constituting a leading edge, and screen means extending outwardly from the trailing edges of said gutter and substantially co-extensive therewith to reduce the local velocity in a zone of the stream laterally adjacent said trailing edges whereby a gradual velocity gradient is produced and maintained between the' local and main stream velocities along substantially the entire lengths of said trailing edges.

prisinga relatively coarse screen and a relatively fine screen, -sa1d relatively coarse screen extending further from said trailingedge than said relatively fine screen.

6.'The apparatus of claim 3, said' screen means extending, directly outwardly from said trailing edges and transversely of the direction of gas flowJ 7 The apparatus of claim 6, said screen means com:

prising a relatively coarse screen and a relatively fine screen, said relatively coarse screen extending further from saidftrailing edge'than said relatively fine screen.

8.; The apparatus of claim 3, said screen means extending from said trailing edges and lying substantially in the planes of the sides ofsaid V-shaped gutter and comprising a relatively coarse screen and a relatively fine screen, 'saidf relatively-coarse screen extending further from said trailing edge than said relatively'fine screen.

9. In a jet engine, a flame stabilizer comprising a'V- shaped gutter extending transversely of a high velocity gas stream, the apex of said gutter constituting a leading edge,

of said leading edge extending screen, said relatively coarse screen extending further from said leading edge than said relatively fine screen;

References Cited in the tile of this patent UNITED STATES PATENTS Y 2,447,482 Arnold Aug. 24, 1948' 2,679,137 Probert May 25, 1954 2,714,287 Carr Aug. 2, 1955 laterally outwardly V 

